Apple has come under fire after changes to the iTunes App Store led Amazon to alter its Kindle app.

The changes, which were first announced in August but only introduced on June 30, saw app developers being required to hand over 30 percent of cost of any content they sold via an app hosted in the iTunes app store. As a result, Amazon removed a link to the Kindle Store in the app that allows iPhone and iPad users to download and read ebooks on their iOS device.

Now, users must exit the app and head directly to the Kindle Store to purchase eBooks to read on their iPhone or iPad.

A number of users voiced their concerns about the changes to the app on its page in the iTunes app store.

One user, James Bisset, said: "The app is great, at least till they had to remove the 'Store' button. This is due to Apple's policy". Meanwhile, Salwinder added: "For those complaining about the Kindle store button being removed – blame Apple. They forced Kindle and other reading apps to remove any direct links to their own stores - Apple claimed this was a breach of terms and conditions."

Apple has yet to comment on the matter.